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Strange observations with application of high voltage to 25 watt light bulb

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Nah

Thu Jun 09 2011, 07:25PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Hello!

A 10kilovolt, 23 miliamp AC voltage source was applied to a 25 watt, incandensent lightbulb. The filliment inside started vibrating at a very fast rate. Any opinions on why this is happining? I have some ideas, but I want to see what our members have in mind.
Thank you

Paul

radiotech

Thu Jun 09 2011, 08:45PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

To start off: What is the frequency?, Was the current 0.023 A through the filament. If it was , for a 25 watt 120 volt lamp, there would have been
13 volts across it, enough for a feeble glow in a dark room.

From there, what was geometry of filament?

Forces? Earth Bfield? 1/4 gauss. Skin effect thermals?

What filler gas if any?

Precise waveform of the voltage as measured at lamp terminals?]

Nah

Thu Jun 09 2011, 09:40PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

60hz

half of the output was grounded.

filiment was in a rectangular form

I don't think that you need that much info, are you pulling my leg?

Normal light bulbs are argon filled, if I remember

JKowalski

Thu Jun 09 2011, 11:32PM

Registered Member #3595 Joined: Mon Jan 10 2011, 04:46AM
Location:
Posts: 26

I would think it would be ion wind - the trace gases in the bulb are being ionized and the spring-ish filament is being repelled from these gases... The spring action of the filament establishes some resonance over time...

Xray

Fri Jun 10 2011, 12:20AM

Registered Member #3429 Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288

Nah wrote ...

Hello!

A 10kilovolt, 23 miliamp AC voltage source was applied to a 25 watt, incandensent lightbulb. The filliment inside started vibrating at a very fast rate. Any opinions on why this is happining? I have some ideas, but I want to see what our members have in mind.
Thank you

Paul

You need to give more details. When you state: A 10kilovolt, 23 miliamp AC voltage source was applied to a 25 watt, incandensent lightbulb. What do you mean by "applied"? Was it across the filament, or did you simply connect one terminal of the transformer to one filament contact, so that the gas inside the bulb could ionize through capacitive coupling with the surrounding air? Also, was it a frosted or clear lightbulb? Others may want to attempt to duplicate what you did, and so every detail is important.

Nah

Fri Jun 10 2011, 07:58PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

One terminal was conected to one side to the light bulb, the other to ground.

Clear light bulb, if it was frosted, I couldn't have see the filiment!

I think j is spot on with the ionic wind thing, that was my theory.

On the other side, my transformer burnt out

However, it is the older, non potted type, so I think I can repair it.

klugesmith

Fri Jun 10 2011, 08:32PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Xray wrote ...

Nah wrote ...
A 10kilovolt, 23 miliamp AC voltage source was applied to a 25 watt, incandensent lightbulb.

Yes, seriously, we need to know more.
To begin with, technically, is it a 10kV voltage source or a 23 mA current source? Can't be both.
Perhaps you are talking about a NST with "10KV" and "23MA" on the nameplate. An electrical circuit model for that is neither a voltage source nor a current source.

radiotech

Sat Jun 11 2011, 05:14AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Google Barkhausen effects in type S1 fillament lamps,
to see why geometry is an issue.

Also, although you wont find it, more than 100 years ago, lightbulbs
were investigated because thermal characteristics were found to be
producing reactance-like effects.

Light bulbs are complex and , are terrible noise sources,
and cannot be easily modeled. The can produce sound, and act as microphones.

The filler gas is used to cool the filament, and without it the
tungsten would evaporate and blacken the bulb.

The filament can pull metallic ions through the glass
of a lighted lamp and cause them to coat the inner surface of the lamp.

Nah

Sat Jun 11 2011, 06:28PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Radiotech,

Isn't that just the Edison effect?

If I remember correctly, Edision found that electrons were bombarding the inner surface of the bulb, carrying carbon with it. This was the genisis of the vacuum tube. Or are you taking about something different?

Guys, I am a pratical man. When I talk about a 10kilovolt, 23 miliamp voltage source, I am taking about a power supply (In this case a 60hz transformer) that outputs 10 kilovolts at a max of 23 miliamps. I understand that that may be a little confusing, and I apologize for that.

Please, ask any questions you like and I will look up the Barkhausen effect. It looks to be very interesting from a quick glance of it.

klugesmith

Sat Jun 11 2011, 08:00PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Nah wrote ...
Guys, I am a pratical man. When I talk about a 10kilovolt, 23 miliamp voltage source, I am taking about a power supply (In this case a 60hz transformer) that outputs 10 kilovolts at a max of 23 miliamps. I understand that that may be a little confusing, and I apologize for that

I'm practically interested in trying to duplicate your experiment, which is the reason for asking about particulars. Not trying to be pedantic.

Are we talking about a 60 Hz neon sign transformer with 10kV 23mA on the nameplate,
or "a power supply that outputs 10 kilovolts at a max of 23 miliamps"?
Ordinary NST's can never deliver their rated voltage at their rated current (their nameplates are weird about that).
The rated voltage is for an open circuit. The rated current is that at which the output voltage has dropped to zero (short circuit case). Intermediate currents give intermediate voltage reduction; normal lighted neon signs are much closer to the short-circuit than the open circuit.

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